Skype killing sound

When ever i want to get on skype It kills the sound. i cant hear anything. I turn on skype the sound to myspeakers are cut and i cant listen to stuff on itunes the internet or any of my games. can you help me out cause i really want to chat with people but i cant with out my sound. I think it stops my mic too... I have to restart every program again just cause skype came up on my computer